Industrial fabrics used in filtration, conveyance and similar processes are typically manufactured by means of a weaving process whereby natural or synthetic yarns are interwoven to provide either the entire fabric, or only a base portion which may subsequently be either encapsulated (e.g. with polyurethane or other similar rugged material) or needled to attach a nonwoven batt material. Such fabrics have been satisfactory for these uses, but the cost of their production is high, particularly when the fabrics must be finely and precisely woven using relatively small yarns. Further, these fabrics must be rendered endless in some manner, either by installing a seaming element at their opposed longitudinal ends, or by re-weaving the longitudinal yarns back into the fabric structure to form seaming loops or similar joining means, for secure connection by a pintle, coil or similar securing means. It is also known to weave such fabrics in an endless manner, so that there is no seam, or to interweave the yarns from one longitudinal end into the yarns of the opposed end to form a woven seam. These fabrics are expensive to produce and require a high capital investment in wide industrial looms and similar related equipment for subsequent processing, as well as a skilled workforce to operate the equipment and produce an acceptable finished product.
It is also known to make these industrial fabrics from film or other continuous media, and to provide perforations, profiling or other treatment prior to assembly. See for example WO 2010/088283, WO 2010/088280, WO 2010/068778, WO 2010/068765, WO 2010/030570, WO 2010/030547 and WO 2010/030298, all commonly assigned to Albany International Corp., which disclose various industrial fabrics formed from a film and which are intended for use in the manufacture of various sheet-like products. In general, the fabrics disclosed in these references are comprised of a film which has been laser drilled for porosity; their surfaces can be patterned to provide grooves or various topographical features, and may also be treated for static dissipation or contamination resistance. The film can be comprised of any thermoplastic however PET is preferred; two or more layers of the same of differing material can be laminated together and reinforcing fibers can be included within the structure.
GB 2,202,873 and GB 2,235,705 (both to Lefkowtiz) disclose paper machine fabrics, in particular press felts, having knuckle-free surfaces which include parallel machine-direction yarns laid in a single plane and subsequently embedded in a sheet of polymeric material such as polyurethane or fluorinated polymers; the sheet, yarns and embedding matrix are then perforated to allow drainage and a batt material may subsequently be attached to one or both surfaces of the resulting textile.
Other paper machine clothing into which a film-like component has been incorporated are described in various patents, for example U.S. Pat. No. 6,071,837 (Crook), U.S. Pat. No. 6,436,240 (Jeffrey), U.S. Pat. No. 6,531,418 (Lidar et al.), U.S. Pat. No. 6,989,080 (Hansen), U.S. Pat. No. 7,323,087 (Beck). It is also known from U.S. Pat. No. 7,029,264, U.S. Pat. No. 7,303,861 and U.S. Pat. No. 7,713,683, all to Gray et al., to provide an apparatus for making a formed polymeric film by passing jets of high pressure water through apertures so as to deform the film. However, the films require the use of reinforcing yarns within the film extrusion.
Other apertured films, and processes for their manufacture, to provide textiles for various industrial applications, are known. For example, U.S. Pat. No. 4,842,794, U.S. Pat. No. 5,207,962, and U.S. Pat. No. 5,262,107 all to Hovis et al., disclose fabrics and processes for forming same including an apertured thermoplastic film which has been deformed by means of a patterned embossing roll. U.S. Pat. No. 6,623,586 (Mortellite et al.) discloses a product and apparatus for lamination of a polymer film into a sheet of web material. U.S. Pat. No. 5,916,462 (James et al.) discloses a method of forming an apertured support member by moving a laser in a series of raster scans over the surface of a workpiece to drill one or more apertures which are surrounded by a plateau. U.S. Pat. No. 6,700,036 (Thomas et al.) discloses an absorbent article including an “acquisition distribution layer” formed from a three dimensional apertured film. U.S. Pat. No. 7,722,588 (Johnson et al.) discloses a multilayered apertured film for use in thermal sealing processes for formation of an absorbent article. U.S. Pat. No. 7,589,249 (Gubernick et al.) discloses an apertured web comprising multiple discrete zones of land arrangements and at least two apertures. JP 2002/113775 (Dai Nippon Printing) discloses a process for producing an uneven plastic sheet including convex lens formations.
However, none of the references noted above discloses a fabric having the advantageous properties of woven fabrics, for industrial filtration and similar uses, and which is constructed from one or more layers of a polymer film which has been contoured by providing a combination of an embossing or similar process to raise portions of the film above its general plane to form protrusions, and slit to create apertures at the raised portions.
It would therefore be highly desirable to provide a simple, relatively less expensive process for the use of such polymer film for the construction of nonwoven fabrics possessing most or all of the advantageous properties of the known woven industrial fabrics, without the disadvantages and cost of the steps required to produce such woven fabrics.